The principal objective of this study is to determine the effect of ethanol on the metabolism of neurosteroids in the central nervous system. Neurosteroids such as 5a-pregnane-3a-ol-20-one (5a,3a-THP or Allopregnanolone) and 5a-pregnane-3a,21-diol-20-one(THDOC) have been shown to modulate the GABA/benzodiazepine binding sites and to exert anxiolytic and hypnotic effects. Modulation of these neurosteroids in the central nervous system by ethanol may be one of the underlying mechanisms for stress observed in human alcoholics especially during withdrawal. The GC/MS-NCI technique that we previousely established for the measurements of trace levels of neurosteroids in human cerebro spinal fluids (CSF) has been improved to include the analysis of progesterone and dihydroprogesterone, and extended to the analysis of human and rat plasma samples in this period. We were able to quantitate pregnenolone, 5a,3a-, 5b,3a-, 5a,3b-THP, androsterone and dihydrotestosterone, dihydroprogesterone and progesterone in those samples. Using this technique, we participated in the development of a pseudopregnancy model of catamenial epilepsy by NINDS investigators. Investigations on the effect of progesterone metabolism on post-partum depression are now in progress in collaboration with NIMH.